For a long time the indissoluble nature of marriage and the gender distribution of social roles was met by payment of (lifetime) alimony after the divorce : the man had to provide an income for his ex-wife, independently of the amounts paid for bringing up their shared children. In France, this legal model was partially abandoned in 1975 with the setting up of a “compensatory allowance”. This meant, instead of a paying a maintenance allowance, making a payment of capital which was supposed to compensate for the disparity in standards of living at the time of separation and for the foreseeable future. This law did not however put an end to lifetime allowances and it was followed by a series of reforms aimed at both encouraging capital payments and limiting the accepted amounts. This movement is evidence of the idea of formal equality between spouses and strengthens the principle of a “single settlement” at the time of the divorce. The time of “unmarriage” is now established, but not that of the equality of the sexes : in parallel with greater participation of women in the employment market and the decline in the fertility rate, we know that investment in domestic activities and the children’s upbringing, the advancement of both professional careers and incomes for men and women remain very different. However, whilst the social conditions for its payment seem still to exist, a compensatory allowance is rarely claimed during divorce proceedings and only 12.5% of divorce decisions include one, in parallel with a constant decrease in the amounts granted. Moreover, the criteria for decision given to judges by the Civil Code remain ambiguous and still fluctuate between the principle of alimony (ensuring the ex-wife minimum resources) and that of compensation or benefit (compensating for the wife’s loss of earnings linked to her domestic investment to the detriment of her professional investment). Consequently, it is not possible from the decisions rendered to understand the principles determining the amount of compensatory allowances. We therefore seek to know the determinants for the judge in allocating an amount, and in particular, whether or not they are linked to the existence of such inequality in the couple, given that practitioners are starting to use “scales” whose criteria remain implicit. Bringing together researchers in law, economics and sociology with practitioners (judges, lawyers), this project aims to investigate the theoretical, empirical and political basis of the payment of such an allowance. It further proposes to scientifically analyse how the practitioners (lawyers, trial court judges, appellate court judges) confront contradictions and ambiguities when they have to make a decision granting and fixing the amount of a compensatory allowance. Finally, from the findings of the preceding analyses, the project’s ambition is to design a decision-making tool to assist in fixing the amount of a compensatory allowance (scale) which can be proposed to the Ministry of Justice.